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Water column oxygen respiration dynamics and quantification of nitrogen cycling genes in sediment of Lake Erie

Niewinski, Desi
http://rave.ohiolink.edu/etdc/view?acc_num=wright1547330489488682

Abstract Details

2018, Master of Science (MS), Wright State University, Earth and Environmental Sciences.
The western basin of Lake Erie experiences annual non-nitrogen (N) fixing harmful algal blooms (HABs), while the central basin experiences seasonal hypoxia in bottom water. In the western basin, water column oxygen respiration rates were quantified at four stations throughout the 2016 and 2017 field seasons, including the proportions of total oxygen consumption accounted for by sediments and by water column nitrification (measured in parallel; Hoffman, unpublished data). Water column respiration rates in the central basin of Lake Erie also were measured in July 2017 during seasonal bottom-water hypoxia. Volumetric water column respiration in the western basin in 2017 (0.011–1.227 mol O2/L/hr) was significantly lower than in 2016 (0.275–1.859 mol O2/L/hr; ANOVA, p < 0.001). In July 2017, western basin respiration rates (0.524 ± 0.124 mol O2/L/hr) were not significantly different from those measured on the same day throughout the central basin water column (0.428 ± 0.089 mol O2/L/hr). Lower rates of water column respiration and sediment oxygen demand (SOD), measured in parallel (Boedecker, 2018), in 2017 coincided with a larger contribution of cyanobacteria to the phytoplankton community relative to 2016. The contribution of nitrification to water column oxygen consumption in the western basin was significantly lower than reported in a previous study. Microbially-mediated transformations occurring in aquatic sediments contribute to in situ N concentrations and availability for primary producers, including cyanobacterial HAB organisms performing photosynthesis. Sediment subsamples were collected in the western basin of Lake Erie in 2016 and 2017, and DNA was extracted to quantify functional gene copies as a proxy for the abundance of microbes capable of denitrification (nirS), N fixation (nifH), and dissimilatory nitrate reduction to ammonium (DNRA; nrfA). The gene copy abundance of nirS was significantly correlated (p = 0.002) with denitrification rates measured in parallel (Boedecker, 2018), and nifH gene copy abundance was significantly correlated with sediment N fixation rates (Boedecker, 2018) at two sites (p = 0.003). However, nrfA gene copy abundance was not correlated to DNRA rates, calculated by proxy using the nitrate-induced ammonium flux (Boedecker, 2018). These molecular analyses help corroborate the parallel geochemical rate measurements and confirm the genetic capability of microbial pathways in these sediments.
Silvia Newell, Ph.D. (Advisor)
Mark McCarthy, Ph.D. (Committee Member)
Chad Hammerschmidt, Ph.D. (Committee Member)
104 p.
Biogeochemistry
Lake Erie sediment; harmful algal blooms; HAB; seasonal hypoxia; water column oxygen respiration; nitrogen cycling; water column nitrification; water column respiration; sediment oxygen demand; SOD

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Citations

  • Niewinski, D. (2018). Water column oxygen respiration dynamics and quantification of nitrogen cycling genes in sediment of Lake Erie [Master's thesis, Wright State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=wright1547330489488682

    APA Style (7th edition)

  • Niewinski, Desi. Water column oxygen respiration dynamics and quantification of nitrogen cycling genes in sediment of Lake Erie. 2018. Wright State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=wright1547330489488682.

    MLA Style (8th edition)

  • Niewinski, Desi. "Water column oxygen respiration dynamics and quantification of nitrogen cycling genes in sediment of Lake Erie." Master's thesis, Wright State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright1547330489488682

    Chicago Manual of Style (17th edition)

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This open access ETD is published by Wright State University and OhioLINK.